The present invention relates generally to satellite communication devices, and more particularly to a call routing interface for satellite communications user terminals.
Mobile communication systems have proven very popular in the Untied States, as well as in other countries. However, some mobile communications systems, such as cellular telephone systems, serve only limited geographic locations. In addition, there are a wide variety of cellular communications protocols, not all of which are compatible. In an effort to provide greater mobility, satellite-based communications systems have been developed.
One example of a satellite communications system is a system called Asia Cellular Satellite (ACeS). In ACeS systems, a user communicates over the satellite communications system via a user terminal. The user terminal communicates with a satellite orbiting the earth which, under the direction of the Network Control Center (NCC), forwards the communication signal to an appropriate xe2x80x9cgatewayxe2x80x9d near the destination. The gateway is the portion of the satellite communications system which, among other functions, provides connectivity to external communications networks such as the Public Switched Telephone Network, Public Land Mobile Networks, and private terrestrial networks. From the destination gateway, the call is routed to the ultimate destination.
It is important in satellite communications systems that calls be routed to the proper gateway so that the system may operate efficiently and costs may be minimized. The assignment of a call to a particular gateway is based on information exchanged between the satellite communications user terminal and the NCC during a procedure known as call initiation.
Typically, the call initiation procedure in a satellite communications system has two main steps: channel request, which primarily involves the user terminal and the NCC, and call setup which primarily involves the user terminal and the destination gateway. During channel request, the user terminal transmits a call initiation signal to the satellite which routes the signal to the NCC. Included in the call initiation signal is information relating to the type of service required and information relating to which gateway should be used. The term xe2x80x9cgateway selection informationxe2x80x9d will be used herein to refer to the information relating to which gateway should be used. Typically, gateway selection information includes a country code and national destination code. The country code and national destination code typically form a portion of the complete address of the destination, typically referred to as the destination routing information. That is, the country code and national destination code typically are a portion of the complete phone number for a particular destination. The complete destination routing information typically includes a country code, a national destination code, and a subscriber number. In some instances, the gateway selection information may alternatively include a Mobile Country Code (MCC) and Mobile Network Code (MNC). Based on the gateway selection information, the NCC selects the appropriate gateway to manage the communications session. Once the appropriate gateway has been determined, the second step, call setup is entered. In call setup, management of the communications session is typically turned over to the gateway and the NCC for all practical purposes is removed from the communications pathway. The operational details of satellite communications systems, including ACeS systems, are well known in the art and are not further discussed herein except as necessary for understanding of the present invention.
In traditional phone systems, the entry of a partial destination phone number without a country code is presumed to indicate that the destination country code is the same as the originating country code. Likewise, the absence of a national destination code implies that the destination national destination code is the same as the originating national destination code. That is, if a number such as 555-1234 is dialed, the call will be treated as xe2x80x9clocalxe2x80x9d and the destination will be assumed to be the subscriber having the subscriber number 555-1234 and the country code and national destination code of the originating location. This assumption is possible because communications originating from fixed land-line phones, terrestrial cellular phones, or similar terrestrial networks originate through a given switching center having a known location. Hence, the country code and national destination code of the destination may, in effect, be supplied by the other portions of the communications system (other than the user terminal) if not supplied by the user. Thus, traditional phone systems may assume that the destination switching center is the same as the originating switching center unless told otherwise by the user.
In contrast, present satellite-based mobile communications systems are not designed to assume that the destination gateway is the same as the originating gateway, quite simply because there is only one originating gatewayxe2x80x94the NCCxe2x80x94in all instances, but a myriad of possible destination gateways. A satellite communications user terminal communicates directly with a satellite, orbiting above the earth""s surface. The user terminals are typically designed to be mobile and are further designed to be used from a variety of countries, meaning that the satellite communications user terminal may be making direct contact with the satellite from a wide variety of locations. Neither the satellite nor the ground segments of the satellite system necessarily know the location of the user terminal. As such, assumptions about what country codes and national destination codes are xe2x80x9clocalxe2x80x9d to the user terminal are inappropriate. Accordingly, the user terminal must provide gateway selection information during call initiation so that the satellite communications system may select the proper gateway to handle the call, even if the call is xe2x80x9clocal.xe2x80x9d If such gateway selection information is not provided during the channel request portion of call initiation, the call initiation attempt typically fails.
Providing the gateway selection information presents difficulty for some users who are more accustomed to the reactions of a Public Switched Telephone Network (PSTN) or a cellular telephone system. Because such PSTN or cellular systems allow connections to be made with less than complete destination information, due to the assumptions discussed above, some users are not accustomed to being required to enter the equivalent of gateway selection information in order to successfully complete a call. Moreover, phone numbers stored in the phone book of the user terminal are normally in the format appropriate for PSTN or terrestrial cellular systems, i.e. without a complete equivalent of the gateway selection information. But current satellite-based systems need gateway selection information during call initiation in order to function properly. It is believed that user satisfaction would be improved for satellite communications user terminals if the call routing interface was more like the interface used for cellular telephones in terrestrial systems. Accordingly, there is a need for an improved call routing user interface for satellite communications user terminals.
The present invention provides an improved user interface for satellite communications user terminals in satellite communications systems for providing call routing information. In one approach, a symbol, for example a key on a keypad, is associated with gateway selection information, such as a country de and national destination code. A user thereafter initiates a call by selecting the symbol and causing a subscriber number for the destination to be entered. Thereafter, the satellite communications user terminal automatically transmits the gateway selection information associated with the symbol during the channel request portion of call initiation. In another approach, some gateway selection information is selected as a default. Thereafter, the satellite communications user terminal automatically transmits the default gateway selection information, when appropriate, during the channel request portion of subsequent call initiations until the default is changed. Using the present invention, gateway selection information is supplied by the satellite communications user terminals to the satellite communications system during channel request via a user interface that is more similar to terrestrial communications systems. User satisfaction with satellite communications user terminals is thereby improved.